Perovskite oxides extended defects

There is little doubt that many materials that at present are described as containing ordered arrays of point or extended defects will be successfully described as notionally defect-free modulated structures. For example, the intergrowth Aurivillius phases, described as containing extended planar defects, have recently been described compactly as modulated structures. " The same formalism has been applied to hexagonal perovskite structures and superconducting copper oxides. Others will certainly follow. 

Factors determining an enhanced activity of MA perovskites are elucidated the most important appears to be an Increased density of extended defects and surface segregation of the microphases of transition metal oxides. 

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